CXCL13 drives spinal astrocyte activation and neuropathic pain via CXCR5
Bao-Chun Jiang, … , Ru-Rong Ji, Yong-Jing Gao
Bao-Chun Jiang, … , Ru-Rong Ji, Yong-Jing Gao
Published January 11, 2016
Citation Information: J Clin Invest. 2016;126(2):745-761. https://doi.org/10.1172/JCI81950.
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Research Article Neuroscience

CXCL13 drives spinal astrocyte activation and neuropathic pain via CXCR5

Abstract

Recent studies have implicated chemokines in microglial activation and pathogenesis of neuropathic pain. C-X-C motif chemokine 13 (CXCL13) is a B lymphocyte chemoattractant that activates CXCR5. Using the spinal nerve ligation (SNL) model of neuropathic pain, we found that CXCL13 was persistently upregulated in spinal cord neurons after SNL, resulting in spinal astrocyte activation via CXCR5 in mice. shRNA-mediated inhibition of CXCL13 in the spinal cord persistently attenuated SNL-induced neuropathic pain. Interestingly, CXCL13 expression was suppressed by miR-186-5p, a microRNA that colocalized with CXCL13 and was downregulated after SNL. Spinal overexpression of miR-186-5p decreased CXCL13 expression, alleviating neuropathic pain. Furthermore, SNL induced CXCR5 expression in spinal astrocytes, and neuropathic pain was abrogated in Cxcr5–/– mice. CXCR5 expression induced by SNL was required for the SNL-induced activation of spinal astrocytes and microglia. Intrathecal injection of CXCL13 was sufficient to induce pain hypersensitivity and astrocyte activation via CXCR5 and ERK. Finally, intrathecal injection of CXCL13-activated astrocytes induced mechanical allodynia in naive mice. Collectively, our findings reveal a neuronal/astrocytic interaction in the spinal cord by which neuronally produced CXCL13 activates astrocytes via CXCR5 to facilitate neuropathic pain. Thus, miR-186-5p and CXCL13/CXCR5-mediated astrocyte signaling may be suitable therapeutic targets for neuropathic pain.

Authors

Bao-Chun Jiang, De-Li Cao, Xin Zhang, Zhi-Jun Zhang, Li-Na He, Chun-Hua Li, Wen-Wen Zhang, Xiao-Bo Wu, Temugin Berta, Ru-Rong Ji, Yong-Jing Gao

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Figure 1

CXCL13 is upregulated in spinal neurons after SNL and contributes to SNL-induced neuropathic pain.

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CXCL13 is upregulated in spinal neurons after SNL and contributes to SNL...
(A) The time course of Cxcl13 mRNA expression in the ipsilateral dorsal horn from naive (n = 6), sham, and SNL-operated mice. SNL increased Cxcl13 expression at 1 day (n = 3), 3 days (n = 5), 10 days (n = 3), and 21 days (n = 5) compared with sham 1 day (n = 5), 3 days (n = 3), 10 days (n = 3), and 21 days (n = 5), respectively. *P < 0.05; ***P < 0.001, Student’s t test. (B) ELISA shows increased CXCL13 protein levels in the ipsilateral dorsal horn after SNL (n = 4) compared with sham (n = 5) or naive (n = 5) animals. ***P < 0.001, Student’s t test. (C) ELISA shows CXCL13 protein increase in the CSF of mice with neuropathic pain (n = 9) compared with sham (n = 7) or naive mice (n = 8). *P < 0.05, Student’s t test. (D–F) Representative images of CXCL13 immunofluorescence in the L5 dorsal horn. CXCL13 IR was low in naive mice (D), but increased in the ipsilateral dorsal horn (E) compared with the contralateral dorsal horn (F) 10 days after SNL. Scale bars: 100 μm. (G–K) In situ hybridization of Cxcl13 mRNA and immunofluorescence staining of NeuN (G–I), GFAP (J), and Iba-1 (K) shows that Cxcl13 mRNA was colocalized with neuronal marker, but not with markers of astrocytes or microglia. Scale bars: 50 μm; 10 μm (insets). (L) Double staining of CXCL13 and neuronal marker MAP2 in cultured dorsal horn neuron. Note the distribution of CXCL13 in neurite terminals (arrows). Scale bar: 25 μm. (M and N) Inhibition of Cxcl13 by shRNA lentivirus (n = 9) attenuated SNL-induced mechanical allodynia (M) and thermal hyperalgesia (N) compared with LV-NC treatment (n = 8). Intraspinal injection was performed 3 days after SNL (arrows). *P < 0.05; **P < 0.01; ***P < 0.001, 2-way repeated measures ANOVA followed by Bonferroni’s test.